Polypropylene resins have low specific gravity, high rigidity and good molding properties and are therefore used as various structural parts such as convenience goods, kitchen accessories, home appliances, machine parts, electrical components and automotive parts.
Structural parts used around automobile engines or electrical components such as fans of air conditioner outdoor units are subjected to stress during use sometimes at high temperatures. Accordingly, the structural parts require high vibration fatigue resistance. To reduce deformation under stress, propylene resin compositions are used which are blends of polypropylene and fillers such as talc and glass fibers. Against the backdrop that the use duration of products should be extended, a prolonged life of propylene molded articles is desired. JP-A-2004-002837 and JP-A-2003-321555 disclose that vibration fatigue strength is improved by increasing the molecular weight of polypropylene resin phases. Although vibration fatigue strength is improved by increasing the molecular weight of polypropylene resin phases, flowability during molding is lowered at the same time and it is therefore difficult to adopt this method to the manufacturing of large molded articles.    Patent Document 1: JP-A-2004-002837    Patent Document 2: JP-A-2003-321555